Ultrasonic energy is applied to produce vibrations or pulses within particles and solid materials usually at frequencies that vary between 20 and 60 KHz, when the sound waves that are transmitted through liquids reach acoustic wavelengths of 7.5 cm to 0.015 cm (speed of sound in liquids: 5,000 feet/sec.=1,500 m/sec.).
The most important mechanism related to ultrasound interacting with solid materials immersed in a liquid phase is called cavitation; a process which forms bubbles loaded with gas. The dynamic actions caused by the expansion (negative pressure) and compression (positive pressure) of the acoustic waves when the sound passes through a liquid, cause the bubbles to collapse. The collapse of the bubbles, in the inner part of which there exists a high vacuum, generates energy through implosion or violent burst and cause the following effects:
1. It fractures the gangue matrix associated with the ore at the zones of lower resistance which is usually at the interfaces of the different compositions or components of the ore. The fracture liberates selectively fragile compounds from the ore without alteration, consequently increasing significantly, the diffusion speed of a leaching reagent. Gangue matrix means commercially worthless mineral matter in the ore. A leaching reagent is any reagent used for dissolution of a metal contained in an ore, and the dissolution is achieved by diffusion of leaching reagent through metallic particles until these are brought into solution. The acoustic forces are practically the principal force that fracture the particles, liberating the surface contaminants.
2. It produces heat in the form of hyperhot points that obviously increase the ore extraction as well as vapor dissolution with the new temperature gradient, thereby reducing the reaction time without diminishing the extraction percentage.
Thus, for instance, the U.S. Pat. No. 4,443,322 relates to a continuous process and device to separate hydrocarbons or oils from sand or clay particles, breaking the solids to particle sizes that can be suspended in water as carriers in such a way that such suspension can be pumped up through an inclined duct or separator, where the suspended particles are submitted to ultrasound vibrations within a range of 18 to 27 KHz.
Other techniques to separate hydrocarbon liquids and produce gases, such as methane, carbon dioxide, etc., applying ultrasonic methods to aqueous media, are known.
The application of ultrasound in a hydraulic reactor and classifier to effect a continuous and more efficient separation and recovery of desired materials, minerals or chemical compounds, however, has not been devised.
It is thus an object of the present invention to offer a separator and classifier reactor that can extract minerals of interest through the use of sound waves which utilize the differential solubility of the minerals, with frequencies within a range of 20,000 Hz to 10 MHz.
A further object of the present invention is to offer an equipment that cam work as a static classifier for solid particles, a flotation cell, a separator and a reactor for solid-liquid reactions where catalytic effect of chemical reactions and flotation is required.
There are three functions performed by the equipment: a) as a static classifier, which is explained in the invention; b) as a leaching reactor, in which it can extract values of interest from minerals through the use of sound waves, enhancing the differential solubility of mineral particles with different sizes; and c) as a flotation cell.
Hereinbelow, the present invention will be described according to the drawings of FIG. 1 in order to define the invention more clearly but, obviously without limiting its scope.